Interlock between circuit interrupters and drawout fuse drawers of indoor power center

ABSTRACT

An interlock between fuse drawout drawers and circuit interrupters of an indoor power center has cams rotatable by the circuit interrupter operating members to actuate cam followers having enlarged diameter portions, a rocking bar operatively connected adjacent its ends to the cam followers, and a stationary stop positioned intermediate the ends of the rocking bar to permit pivoting of the rocking bar by a cam follower when either operating member is actuated to close a circuit interrupter but to interfere with transverse translation of the rocking bar and thus prevent displacement of both cam followers when the operating members are actuated in an attempt to close both switches simultaneously. Ganged interfering arms are rotatable between positions wherein they obstruct withdrawal of the fuse drawers and wherein the fuse drawers may be withdrawn, and means for preventing closure of either circuit interrupter when a fuse drawer can be withdrawn and for preventing withdrawal of a fuse drawer when either circuit interrupter is closed includes a longitudinally reciprocable interlocking bar having keyhole openings receiving said cam followers and parallel crank linkage means operatively connecting said interfering arms and said interlocking bar.

United States Patent Thomas H. Keogh Pittsburgh;

Adolph E. Krupit, Allison Park, Pa. [21] Appl. No. 768,817

[22] Filed Oct. 18,1968

[72} Inventors [45] Patented Feb. 9, 1971 Y [73] Assignee Allis-Chalmers Manufacturing Company Milwaukee, Wis.

[54] INTERLOCK BETWEEN CIRCUIT INTERRUPTERS AND DRAWOUT FUSE DRAWERS 01F INDOOR POWER CENTER 14 Claims, 21 Drawing Figs. [52] U.S. Cl 200/50, 317/114 ;200/153 [51] lnt.Cl H01h 9/26, H01h 9/22 [50] Field ofSearch ZOO/50.15,

50.3.l53.l3;3l7/114,116,103(Cursory); ZOO/50.1; 74/483(Cursory) FOREIGN PATENTS 1,408,959 6/l965 France Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vandethye ZOO/50(3) ABSTRACT: An interlock between fuse drawout drawers and circuit interrupters of an indoor power center has cams rotatable by the circuit interrupter operating members to actuate cam followers having enlarged diameter portions, a rocking bar operatively connected adjacent its ends to the cam followers, and a stationary stop positioned intermediate the ends of the rocking bar to permit pivoting of the rocking bar by a cam follower when either operating member is actuated to close a circuit interrupter but to interfere with transverse translation of the rocking bar and thus prevent displacement of both cam followers when the operating members are actuated in an attempt to close both switches simultaneously. Ganged interfering arms are rotatable between positions wherein they obstruct withdrawal of the fuse drawers and wherein the fuse drawers may be withdrawn, and means for preventing closure of either circuit interrupter when a fuse drawer can be withdrawn and for preventing withdrawal of a fuse drawer when either circuit interrupter is closed includes a longitudinally reciprocable interlocking bar having keyhole openings receiving said cam followers and parallel crank linkage means operatively connecting said interfering arms and said interlocking bar.

PATENTEH FEB 9197! SHEET 3 OF 6 Jile fl 5.

PATENIED FEB 91971 SHEET 5 OF 6 val/1416 &

5 5 @XX Wi/J PATENTEDFEB 9l97l 3,562,452

SHEEIBUFS 541. m 2/9 @EZQMM INTERLOCK BETWEEN CIRCUIT INTERRUPTERS AND DRAWOUT FUSE DRAWERS OF INDOOR POWER CENTER This invention relates to indoor power centers, or unit substations which combine transformers and switchgear to supply electrical power at centers of load from high voltage sources stepped down to service voltage, and in particular it relates to a unitary assembly of terminating means for cables from a plurality of primary feeder sources, circuit breakers for the primary feeders, a transformer, and primary protective equipment for such a power center.

Indoor unit substations, termed power centers, using metalclad switchgear associated with air-insulated or noninflammable liquid-filled transformers are known for application in industrial plants having large floorspace for installation of the substation. Electrical power is usually transmitted at high potential such as 15,000 volts to the power center where it is transformed to supply secondary distribution at 2300 volts or to supply concentrated centers of load with power at service voltages such as 440 volts. Often the functions of transformation, regulation, protection, control and metering of electrical power are combined in a completely enclosed, factory assembled unit substation, but many industrial plants do not have sufficient floor space for such a unit substation, and known components to perform such functions as transformation and control are too heavy and bulky to permit mounting in an overhead location in an industrial plant for the purpose of conserving floor space in the plant.

It is an object of the invention to provide an improved interlock between the circuit breakers and drawout fuse drawers of such an indoor power center which prevents simultaneous operation of both circuit breakers to closed position, prevents operation of either circuit breaker to closed position where a fuse drawer can be withdrawn, and prevents withdrawal of a fuse drawer when either circuit breaker is in closed position.

This and other objects and advantages of the invention will be more readily apparent from the following detailed description when considered in conjunction with the accompanying drawing wherein:

FIG. 1 is a schematic front view of an indoor unitary power center embodying the invention installed in an overhead location in an industrial plant;

FIG. 2 is a front view of the power center shown in FIG. 1 with a portion of the front wall broken away to illustrate the internal construction;

FIG. 3 is a plan view of the apparatus of FIG. 2 with a portion of the cover broken away;

FIG. 4 is a view taken along line IV-IV of FIG. 2;

FIG. 5 is a perspective view of the circuit breakers and bus bar connections between such breakers and the primary fuses of the apparatus of FIG. 2;

FIG. 6 is a view taken along line VI-VI of FIG. 3;

FIG. 7 is an elevation view of the preferred embodiment of the invention taken along line VII-VII of FIG. 3;

FIG. 8 is a view taken along line VIII-VIII of FIG. 7;

FIG. 9 is a view taken along line IX-IX of FIG. 7;

FIG. 10 is a plan view of the preferred embodiment taken along line X-X of FIG. 2;

FIGS. 11 and 12 are perspective views respectively of the fixed and movable fuse trays of the apparatus of FIGS. 29;

FIG. 13 is a view taken along line XIII-XIII of FIG. 3 with the fuse removed;

FIG. 14 is a view taken along line XIV-XIV of FIG. 6 with the fuse removed;

FIGS. 15 and 16 are front and plan views respectively of the fuse tray cover;

FIG. 17 is a view taken along line XVII-XVII of FIG. 15 showing the closed and open positions of the fuse drawer latches in full and in dot-dash lines respectively;

FIG. 18 is an enlarged view taken along line XVIII-XVIII of FIG. 3;

FIG. 19 is a view taken along line XIX-XIX of FIG. 18;

FIG. 20 is a view taken along line XX-XX of FIG. 19; and

FIG. 21 is a view taken along line XXI-XXI of FIG. 6 with a wall of the air circuit breaker removed.

Referring to FIG. I of the drawing, an indoor power center for an industrial plant comprises a power transformer 10, a low voltage circuit breaker 11 for the secondary distribution, and the primary voltage air terminal chamber 12 of the invention mounted on overhead, structural iron trusses 14 that are supported on vertical columns 15 which define a bay of an industrial plant. The indoor power center also includes tap junction boxes 16 which may be mounted on trays 17 for the threephase primary feeder cables 18 supported from the roof 19 of the industrial plant. Electrical power may be transmitted throughout the entire industrial plant at 15,000 volts over the three-phase primary feeder cables 18in the trays 17, and junction, or taps are made in the T-junction boxes 16 between the primary feeder cables 18 and primary tap cables 20 and 2] (shown only as single lines in FIG. 1) to transmit power at 15,000 volts to the air terminal chamber 12 mounted on the overhead trusses 14. The high voltage electrical power is converted in transformer 10 from 15,000 volts to desired secondary potential such as 440 volts service voltage or 2300 volts for secondary distribution.

The T-junction box 16 is disclosed in the copending application of Thomas H. Keogh et al., Ser. No. 673,l48, filed October 5, 1967, and having the same assignee as the present invention. r

The primary voltage air terminal chamber 12 for the indoor power center comprises a unitary assembly of terminating means for the primary tap cables 20 and 21, primary circuit breakers 26 and 27 for the primary sources, current limiting fuses 39 for the power center transformer 10, and interlocking means between primary circuit breakers 26 and 27 and the fuses 39 which prevent simultaneous closing of both primary circuit breakers, prevents primary circuit breaker closing when the fuses 39 are removed, and also prevents removal of the fuses 39 when either primary breaker 26 or 27 is closed, and such air terminal assembly 12 occupies only a fraction of the space and weighs only a fraction of any arrangement of known components and is sufficiently small in size and light in weight to permit mounting on overhead trusses 14, thereby resulting in a substantial saving in floor space.

The air terminal chamber 12 is enclosed in a housing 22 (See FIGS. 2, 3, 4 and 6) of right angle prism configuration supported on a suitable base which may include a pair ofelongated, horizontally spaced, structural iron channel members 23 (See FIGS. 2 and 3) disposed below the bottom wall of housing 22 and affixed at their ends by mounting brackets 24 secured to the web portion of a pair of the overhead trusses 14 of an industrial plant. Housing 22 of the primary voltage chamber 12 encloses a pair of three-phase, primary voltage load-break switches, or air circuit breakers 26 and 27 having elongated casings disposed back-to-back with their longitudinal axes in horizontal planes adjacent the bottom of housing 22 and each having three insulating bushings 28 projecting horizontally from the left end thereof and three insulating bushings 29 projecting horizontally from the right end thereof as shown in FIG. 2. The high voltage, three-phase tap cables 20 and 21 from a pair of high voltage sources such as the breakers 26 and 27 respectively.

The air circuit breakers 26 and 27 are opened and closed manually by operating handles 32A and 328 respectively (See FIGS. 2 and 6) accessible from the front of housing 22 to an operator on a catwalk (not shown) in the industrial plant. The power transformer 10 of the load center may include a casing 35 (See FIGS. 3 and 6) supported (by means not shown) on the trusses 14 and having three primary insulating bushings 36 extending horizontally therefrom through an aperture in the rear wall of housing 22 and into the interior of housing 22 and having terminal means 37 thereon which make electrical connection with metallic ferrules 38 on one end of three current limiting fuses 39 disposed horizontally above circuit breakers 26 and 27. Bus bars 42 (See FIGS. 2, 5, 6 and 13) electrically common the corresponding phase terminal means on insulating'bushings 29 extending horizontally from the right end of both circuit breakers 26 and 27 (as seen in FIG. 2) and connect them to pivoted, verticallyextending copper terminal bars 45 resiliently held against metallic ferrules 46 on the op posite end of current limiting fuses 39. The current limiting fuses 39 are supported within movable fuse trays 48 of suitable high dielectric strength insulating material and clamped under pressure between the terminal bars 45 and the terminal means 37 on transformer bushings 36 by elongated insulating rods 49 which normally are resiliently urged against the terminal bars 45. v

The movable fuse trays 48 are affixed by pins 52 (See FIG. 14) to rectangular fuse tray covers 53 to form fuse drawers 54 which are reciprocable horizontally into and out of housing 22 through openings 55 (See FIGS. 13 and 14) in front wall 56 of housing 22 between the normal position shown in full lines, wherein the fuses 39 engage the terminal means 37 on the transformer bushings .36, and the open position shown in dotdash lines in FIG. 6 wherein the fuses 39 may be changed. Interlocking means described hereinafter prevent withdrawal of fuse drawers 54 until the operating handles 32A and 32B of both circuit breakers 26 and 27 are in open position. The insulating rods 49 are reciprocated within movable fuse trays 48 by externally threaded shafts 58 (See FIGS. 13 and 14) engaged within internally threaded openings 59 in rectangular covers 53 and having hand knobs 60 integral therewith external of housing 22. Resilient means for applying axial pressure against each fuse 39 operatively connects shaft 58 and insulating rod 49 and includes a first cup-shaped member 62 affixed to shaft 58 by a snap ring, a smaller diameter second cupshaped member 63 affixed by a snap ring, a smallerdiameter second cup-shaped member 63 affixed by a snap ring to insulating rod 49 and telescoped within first cup-shaped member 62 so their open ends face each other, and a compression spring 64 disposed within the telescoped members 62 and 63.

The fuse drawers 54 are normally locked to housing 22 by U-shaped drawer latches 66 (See FIGS. 15, 16 and 17) having horizontally extending ears 67 which protrude through eyes 68 on rectangular covers 53 and fit behind hook-shaped catches 70 on casing front wall 56. Fuse drawer latches 66 can be lifted to the dot-dash line position shown in FIG. 17 to remove the ears 67 thereon from behind the hook-shaped catches 70, but laterally projecting lugs 71 on latches 66 normally fit behind the rotatable fuse tightening knobs 60 and prevent lifting of latches 66. Ganged interfering arms 73 (See FIGS. 2, 3 and 14) are rotatable about parallel axes and normally disposed in a horizontal interfering position in front of the fuse tightening knobs 60 to prevent rotation thereof in a direction to release pressure on current limiting fuses 39. Until both circuit breaker operating handles 32A and 32B are in the open position, the ganged interfering arms 73 are prevented by interlocking means described hereinafter from being rotated to the vertical open position shown in dot-dash lines in FIG. 2. After the ganged arms 73 are rotated to the vertical open position, the rotatable fuse tightening knobs 60 can be rotated in a direction to move the shafts 58 outward of easing 22 until the knobs 60 are in the dot-dash line position shown in FIGS. 14 and 17 wherein they no longer interfere with lugs 71 on drawer latches 66, thereby permitting the latches 66 to be pivoted upward until the hook portions 67 are out of the catches 70 to allow withdrawal of the fuse drawers 54 to the open position shown in dot-dash lines in FIG. 6. Movement of a shaft 58 outward of casing 22 by rotating hand knob 60 releasesthe pressure with which the compression spring 64 holds the fuse 39 against the terminal means 37 of transformer bushing 36.

The three-phase primary tap cables and 21 have three conductors 75 (See FIG. 3) which may be of 4/0 size each of which is surrounded by concentric layers of insulation 76 (See FIG. 3), semiconductive material 77, and a metallic grounding sheath 78;The insulation and semiconductive layers 76 and 77 are cut back and the edge of the semiconductive material 77 where the equipotentiallinesconcentrate and the voltage gradient is the highest is covered with a mass 79 of mold-able semiconductive material commercially available under the mark AIRSEAL to reduce the voltage gradient at this point. Flexible insulating boots 80 cover the joints between the cable conductors 75 and the bushing terminals and fit snugly at their ends over the bushings 28 and the insulation of the conductors. The cables 20 and 21 have outer layers of cable armor 81 which is cut back and extends into and is locked to a conventional cable terminator 82. The cable terminators 82 extend through vertically spaced cable entrance ports 83 in the left sidewall 84 of housing 22 (as seen in FIGS. 2 and 4) and are affixed to housing 22 with a hermetic seal by a resilient gasket and a nut 85 engaging external threads on cable terminator 82. The grounding sheaths 78 from the three conductors 75 of each tap cable 20 and 21 are electrically connected together internally of housing 22 and to a copper ground pad (not shown) on a wall of housing 22. Housing 22 preferably has a skeletal framework of elongated members such as angle iron members 86 (See FIG. 4), and removable panels 87 in the left end wall and removable panels 88 (See FIG. 3) in the front wall 56 are supported on studs 89 affixed to elongated members 86 to permit ready access to the cable terminations by the workman.

An L-shaped barrier 90 which may be of sheet steel material extending between front and rear walls of housing 22 above upper circuit breaker 26 separates the air circuit breakers 26 and 27 from the current limiting fuses 39. The bus bars 42A, 42B, and 42C have vertical'portions (See FIGS. 5 and 6) which are connected to and electrically common the corresponding phase terminals on the insulating bushings 29 of both air breakers 26 and 27 and are bent over into horizontal portions 92 supported on standoff insulators 94 mounted on barrier 90. The horizontal portions 92A, 92B and 92C (See FIG. 5) of bus bars 42A, 42B and 42C are in the same horizontal plane. The horizontal portion 92A of bus bar 42A is a flat conductive plate electrically connected to vertical bus bar portion 42A, and the portions 923 and 92C of bus bars 428 and 42C are integral therewith and L-shaped and of different lengths and terminate in alignment with portion 92A. Fixed insulating trays 96 of channel cross section for supporting the movable fuse trays 96 of channel cross section for supporting the movable fuse trays 48 extend in a horizontal direction between the front and rear walls of housing 22 and are supported on standoff insulators 97 (See FIGS. 5, 6 and 13) mounted on the horizontal bus bar portions 92B and 92C and by L-shaped brackets 98 (See FIGS. 6 and 13) on the front wall 56 of housing 22. Pivot pins 99 (See FIGS. 5, 6, and 13) extending through the legs of U-shaped hinge brackets 100 secured adjacent the ends of horizontal bus bar portions 92A, 92B and 92C pivotally mount the vertically extending copper terminal bars 45 which abut against the ferrules 46 on current limiting fuses 39. The terminal bars 45 are electrically connected to horizontal bus bar portions 92A, 92B and 92C by flexible copper straps 101.

The insulating rods 49 are operatively connected by radial pins 104 (See FIG. 14) to U-shaped metal brackets 105 carrying insulating shoes 106 which abut against copper terminal bars 45. The terminal bars 45 fall to an inclined position shown in dot-dash lines in FIG. 13 when the fuse drawers 54 are removed, and the insulating shoes 106 extend downward through apertures 107 and 108 in fixed trays 96 and movable fuse trays 48 respectively and actuate the terminal bar 45 upward into engagement with ferrule 46 on current limiting fuse 39 when fuse drawers 54 are again inserted into housing 22. After a fuse drawer 54 is locked to housing 22 by latch 66, hand knob 60 on threaded shaft 58 is then turned until compression spring 64 exerts pressure against insulating shoe I06 and resiliently clamps current limiting fuse 39 between copper terminal bar 45 and tefminal means 37 on transformer insulating bushing 36.

Terminal means 37 have circular metallic movable contacts 103 (See FIGS. l820) which abut against the ferrules 38 on current limiting fuses 39 and have limited universal motion relative to the transformer insulating bushings 36 and provide high current carrying engagement with the ferrules 38 even when fuses 39 are not in exact axial alignment with bushings 36. Conductive studs 109 extending axially from the porcelain insulator members 110 of transformer insulating bushings 36 protrude into axial bores 112 in the movable contacts 103 with a relatively loose fit and are affixed thereto by pins 113 extending radially through arcuate ear portions 115 on movable contacts 103 and extending with a loose fit through an aperture in conductive stud 109, and such loose fit permits limited movement of contacts 103 in two mutually perpendicular directions relative to studs 109. A flexible current transfer copper lead 116 extends through a radial aperture 117 in stud 109, and the ends of flexible lead 116 are bent into loops and secured by suitable means such as silver solder within apertures 118 in movable contact 103 extending parallel to the axis thereof.

Leveling screws 119 (See FIG. 2) may be provided between the bottom wall of housing 22 and the structural iron channels 23 of the housing base to permit leveling of housing 22 and alignment thereof with the transformer casing 35. Short horizontal guide lugs 120 (See FIGS. 3 and 6) welded in a triangular arrangement on transformer casing 35 fit within annular collars 121 affixed on the rear wall 122 of housing 22 to align the transformer bushing terminals 37 with the fuse ferrules 38. Threaded studs 123 on the rear wall 122 of housing 22 protrude through apertures 124 in metallic plates 125 welded to transformer casing 35, and nuts are threaded on the studs 123 to affix transformer casing 35 to housing 22. Cylindrical aligning members 126 disposed within the apertures 124 have oblong axial openings 127 therein (shown in dotted lines in FIG. 3) which receive the studs 123 and are manually rotatable within the apertures 124 to align the studs 123 on housing 22 with the apertures 124 in plates 125. Transformer bushings 36 protrude from a rectangular-in-cross section recess 135 in transformer casing 35, and a gasket 136 (see FIG. 18) may be disposed between the rear wall 122 of housing 22 and the portion of transformer casing 35 defining the recess 135 to prevent entry of dust into housing 22.

The primary voltage, air break circuit breakers 26 and 27 may be commercially available three-phase, three-pole, single throw 600 ampere load break switches rated at 13.2 kilovolts, 40,000 amperes symmetrical make and latch, and 60,000 amperes momentary and sold under the marks ISOLATOR and lSO-QUENSOR. The specific switches do not constitute a part of the present invention and are shown somewhat schematically in FIG. 21 as including three movable tubular porcelain members 137 each of which encloses a first tulip type contact 138 adapted to maintain continuous engagement with an axially extending bayonet contact 128 supported on insulating bushing 29 as porcelain members 137 are reciprocated axially and a second tulip type contact 129 electrically connected to contact 138 and adapted to engage and disengage a bayonet type contact 130 mounted on insulating bushing 28. The porcelain members 137 are reciprocated axially between open and closed position by a spring type stored energy operator 132, shown only in block form, when a switch operating shaft 132A or 132B is rotated by manual movement of switch operating handle 32A or 32B.

The switch operating shafts 132A and 1328 for circuit breakers 26 and 27 carry eccentric cams 140A and 1408 (See FIGS. 6 and 7) respectively interior of housing 22;Cam followers 141A and 1413 affixed to elongated cam follower rods 142 are urged into continuous engagement with cams 140A and 1408 by compression springs 144 which abut at one end against brackets 145 affixed to housing front wall 56 (See FIGS. 7 and and at their opposite end against washers 147 disposed against pins 148 protruding through the rods 142. The cam follower rods 142 protrude through keyhole slots 150 (See FIG. 8) in a vertical, elongated, longitudinally reciprocable interlocking bar 152. Horizontal pins 153 affixed to the interior of housing wall 56 and extending through elongated slots 155 in interlocking bar 152 guide the bar 152 as it reciprocates longitudinally and interlocking bar 152 is normally resiliently urged to its lowermost position. corresponding to the open position of both circuit breakers 26 and 27, by a compression spring 157. Spring 157 surrounds a bolt 158 which slidably extends through an aperture in a horizontal portion 160 at the lower extremity of interlocking bar 152. and the head of bolt 158 abuts against a bracket 159 secured to the front wall 56 of housing 22 to prevent movement of bolt 158. Compression spring 157 abuts at one end against a nut threaded on bolt 158 and at the opposite end against horizontal portion 160 of interlocking bar 152 and urges interlocking bar 152 to its lowermost position.

Cam followers 141 have internally threaded cylindrical portions which receives bolts that bear against the cams to permit adjustment of the interlock. The cylindrical portions of the cam followers 141A and 1418 are oflarger diameter than elongated rods 142 and can protrude through the circular portion of the keyhole slots but cannot protrude through the elongated portion of the keyhole slots 150. The portions of eccentric cams 140A and 1403 of smallest diameter engage the cam followers 14lA and 1413 when circuit breakers 26 and 27 are in the open position, at which time the springs 144 urge cam followers 141 against cams 140A and 1408 so that the cam followers 141 are not within the keyhole slots 150. thereby permitting interlocking bar 152 to be moved vertically upward to allow withdrawal of fuse drawers 54 and fuses 39 from housing 22 as hereinafter described. When either circuit breaker 26 or 27 is closed to electrically connect a high voltage tap cable 20 or 21 through fuses 39 to transformer 10. the largest diameter portion of the eccentric cams 140A and 1408 engages the corresponding cam follower 141A and 141B and pushes it through the circular portion of the associated keyhole slot 150, thereby interfering with upward movement of interlocking bar 152 and preventing withdrawal of fuse drawers 54 from housing 22.

The air terminal chamber of the invention also has interlocking means to prevent simultaneous closing of both circuit breakers 26 and 27, thereby assuring that one high voltage tap cable 20 is never directly connected to the other high voltage tap cable 21. At the end opposite the cam followers 141, each of the elongated rods 142 has an axially spaced pair of pins 162 extending therethrough disposed on opposite sides of a vertical rocking" bar 163 whose midpoint is positioned adjacent a stop pin, or defeater pin 164 affixed to front wall 56 of housing 22. The pins 162 operatively connect elongated cam follower rods 142 to rocking bar 163 while permitting pivotal movement therebetween, and defeater pin 164'allows rocking bar 163 to pivot when one end thereof is moved by an elongated rod 142, but defeater pin 164 interferes with and prevents translation of rocking bar 163 transverse to its axis. When either switch operating handle 32A or 328 is actuated to closed position, thereby rotating the corresponding eccentric cam 140A or 140B and actuating the associated cam follower 141A or 1418 and cam follower rod 142 longitudinally, the rocking bar 163 pivots about defeater pin 164. The other switch operating handle 32A or 32B cannot be operated to closed position thereafter because the defeater pin 164 interferes with translation of rocking bar 163 transverse to'its axis, thereby preventing longitudinal reciprocation of the other cam follower rod 142 and obstructing movement of the associated eccentric cam 140A or 140B. It will thus be appreciated that rocking bar 163 and defeater pin 164 block simultaneous closing of both circuit breakers 26 and 27 and thus positively prevents accidental connection of one primary tap cable 20 or 21 to the other.

Defeater pin 164 extends through an aperture in housing front wall 56 and has a head which is resiliently urged against a cup-shaped projection 166 on wall 56 by a compression spring 167 (See FIG. 9). The compression spring 167 abuts at one end against the interior surface of the cup-shaped projection 166 and at its other end against a washer 168 disposed against a pin extending through defeaterpin 164, and compression spring 167 normally urges defeater pin 164 to the position shown in FIGS. 7, 9 and 10 where it obstructs translation of rocking bar 163 transverse to its length, thereby preventing simultaneous movement of both switch operating handles 32A and 32B simultaneously to the closed position. If it is desired to simultaneously close both circuit breakers 26 and 27, defeater pin 164 is manually pulled against the force of compression spring 167 until defeater pin 164 no longer interferes with transverse translation of rocking bar 163, thereby permitting both cam follower rods 142 to move longitudinally and allowing both eccentric cams 140A and 1408 to rotate to the position wherein the largest diameter portion thereof engages the cam followers 141A and 1418.

Rocking bar 163 is normally disposed within a notch 169 in the end of defeater pin 164 (See FIG. 9). When defeater pin 164 is manually pulled out and both switch handles 32A and 32B are moved to closed position, rocking bar 163 is translated transversely and the end of defeate r pin 164 rests against the rocking bar 163. When one switch handle 32A or-32B is now moved toward open position, the rocking bar 163 is again translated transversely, and defeater pin 164 is urged by spring 167 to the normal position shown in FIG. 9 wherein rocking bar 163 is within notch 169, thereby preventing return of the switch to closed position and requiring that the switch be actuate d to open position,

Notch 169 presents a flat surface to rocking'bar 163 which minimizes the angular movement of rocking bar 163 when one switch handle 32 is moved between open and closed position, thereby assuring that the cam followers 141 are properly located relative to the keyholeslots 150 in interlocking bar 152 and making the interlock more positive.

The upper end of interlocking bar 152 is affixed to the connecting rod 170 of a linkage having three parallel crank arms 172 each of which is pivotally connected to one end of a crank 174. The cranks 174 are affixed to shafts 176 which rotatably protrude through housing front wall 56 and through sleeve bearings 178 affixed to wall 56. Exterior of housing 22, the shafts 176 are secured to the interfering arms 73 which are normally disposed horizontally in front of hand knobs 60 and thus prevent withdrawal of fuse trays 54 from housing 22. One

- interfering arm 73 is provided with a handle 181 (See FIGS. 3,

7 and 10) which permits manual rotation of the interfering arms 73 (which are mechanically ganged through connecting rod 170) from the solid line horizontal position shown in FIG.

2, where they obstruct unthreading of hand knobs 60, to the vertical dot-dash line position shown in FIG. 2 wherein the hand knobs 60 can be rotated to turn the threaded shafts 58 (See FIGS. 13 and 14) in the internally threaded openings 59 in rectangular covers 53, thereby longitudinally translating the insulating rods 49 to release the pressure of springs 64 against current limiting fuses 39 and moving hand knobs 60 to the dot-dash line position shown in FIGS. 14 and 17 where the fuse drawer latches 66 can be lifted (to the dot-dash line position shown in FIG. 17) to remove the ears 67 from behind the hook-shaped catches 70, thereby permitting withdrawal of fuse drawers 54 from housing 22 (to the dash-dot line position shown in FIG. 6).

A bolt 185 threaded through a bracket 186 (See FIGS. 2 and 3) on housing front wall 56 normally interferes with one of the ganged interfering arms 73 and prevents movement thereof from the horizontal position shown in full lines in FIG. 2, where they interfere with outward movement of hand knobs 60, to the vertical position shown in dot-dash lines wherein hand knobs 60 can berotated to free the fuse drawer latches 66 so that fuse drawers 54 can be withdrawn from housing 22 as seen in FIG. 6. When fuse drawers 54 are closed and interfering arms 73 are in their normal horizontal position, the linkage of parallel crank arms 172 and connecting rod 170 is in the uppermost position shown in full lines in FIG. 7, thereby raising interlocking bar 152 to its uppermost position wherein the circular portion of keyhole slots 150 are opposite the cam followers 141A and 1413. It will be appreciated that in this horizontal position of interfering arms 73 and uppermostposition of interlocking bar 152, the eccentric cams I40A and 1403 can be rotated to push the cam followers 141A and 1418 through the keyhole slots 150, and consequently one switch actuating arm 32A or 32B can be rotated from open to closed position to close the corresponding circuit breaker 26 or 27 and connect one high voltage tap cable 20 or 21 through fuses 39 to transformer 10. When either circuit breaker 26 or 27 is closed, the associated cam follower 141A or 1418 protrudes through the circular portion of a keyhole slot [50. thereby obstructing downward movement of interlocking bar 152, preventing mdvemeht of linkage including crank arms 172, obstructing rotation of interfering arms 73 and preventing withdrawal of fuse drawers 54 from housing 22 as long as one circuit breaker 26 or 27 is closed. When the circuit breaker is opened, the associated cam follower 141A or 1418 is removed from the keyhole slot 150, the interlocking bar 152 can be lowered because the cam follower rods 142 slide in the elongated portion of the keyhole slots 150, and interfering arms 73 can be rotated by means of handle 181 to lower the linkage to the lowermost position shown in dot-dash lines in FIG. 7, thereby permitting unthreading'of hand knobs 60 and withdrawal of fuse drawers 54 from housing 22 and also interfering with movement of either circuit breaker 26 or 27 to the closed position by the elongated portion of keyhole slots I50 preventing longitudinal movement of camfollowers 141A and 1413.

While only a single embodiment of the invention has been illustrated and described, many modifications and variations thereof will be readily apparent to those skilled in the art. and consequently it is intended in the appended claims to cover all such modifications and variations thereof which are within the true spirit and scope of the invention.

We claim: 1. An interlock for a pair of circuit interrupters each having a rotatable shaft for actuating it between open and closed positions comprising, in combination: I

a pair of eccentric cams each of which is operatively connected to and adapted tov be rotated by one of said rotatable shafts; a pair of generally parallel elongated rod cam followers; means for resiliently urging each of said cam followers against one of said cams, said cam upon rotation displacing said cam follower rod longitudinally and effecting maximum displacement of said cam follower rod when said interrupter is in closed position and minimum displacement thereof when said interrupter is in open position; 1

an elongated rocking barpivotally connected adjacent its ends to said cam follower rods;

stationary stop means intermediate the ends of said rocking bar for permitting said rocking bar to pivot when either cam follower rod is displaced by the corresponding cam and for preventing translation of said rocking bar in a direction transverse to its length when either cam follower rod is at said maximum displacement, whereby both of said circuit interrupters cannot be closed simultaneously;

means for resiliently urging said cam follower rods against said cams; and

adjusting means extending longitudinally of and threaded to one end of said cam follower rods and engaging said cams for selectively changing the length of said cam follower rods, whereby the position of said rocking bar relative to said stop means may be adjusted. I

2. An interlock for a pair of circuit interrupters each having an operating member for actuating it between open and closed positions comprising, in combination:

a pair of cams each of which is operatively connected to and adapted to be rotated by one of said operating members;

an elongated cam follower rod engaging each said cam, said cam upon rotation displacing said cam follower longitudinally and having a limit position thereon providing maximum displacement of said cam follower when said interrupter is in closed position;

an elongated rocking bar pivotally connected adjacent its ends to said cam followers; and

means including a stationary defeater pin stop member positioned adjacent said rocking barintermediate its length on the side thereof away from said cams for permitting said rocking bar to pivot about said stop member when either cam follower is displaced by the corresponding cam and for preventing transverse translation of said rocking bar when either cam follower is at said maximum displacement, whereby both'of said circuit interrupters cannot be closed simultaneously, said defeater pin stop member being manually retractable to a position wherein it does not interfere with movement of said rocking bar, whereby both of said circuit interrupters can be closed when it is so desired.

3. An interlock for a pair of circuit interrupters each having an operating member for actuating it between open and closed positions and between said circuit interrupters and a fuse drawer reciprocable between open and closed positions comprising, in combination; 7

a pair of cams each of which is operatively connected to and adapted to be rotated by one of said operating members;

a pair of cam followers each of which engages one of said cams, said cam upon rotation displacing said cam follower and effecting maximum displacement thereof when said interrupter is in closed position;

an elongated rocking bar operatively connected adjacent its ends to said cam followers;

stop means intermediate the ends of said rocking'bar for permitting said rocking bar to pivot when either cam follower is displaced by the corresponding cam and for preventing transverse translation of said rocking bar when either interrupter is closed and the corresponding cam follower is at said maximum displacement, whereby both of said circuit interrupters cannot be closed simultaneously, and means responsive to said maximum opening displacement of either of said cam followers for preventing opening of said fuse drawer.

4. An interlock in accordance with claim 3 wherein said means for preventing opening of said fuse drawer includes a member operable manually between a first position wherein said fuse drawer canbe opened and a second position wherein it obstructs openingof said fuse drawer, and wherein said interlock also includes means responsive to said member being in said first position for preventing displacement of either of said cam followers by its associated cam, whereby neither of said interrupters can be closed when said fuse drawer is open.

5. An interlock in accordance with claim 3 between said pair of circuit interrupters and a plurality of drawout fuse drawers reciprocable in a common claim wherein said cams are eccentric and said cam followers are generally parallel elongated rods and are displaced longitudinally by said eccentric cams and are pivotally connected adjacent the ends of said rocking bar and also including means responsive to said. maximum displacement of either of said cam follower rods for obstructing opening of said plurality of drawout fuse drawers.

6. An interlock in accordance with claim 5 wherein said means for obstructing opening of said plurality of fuse drawers is operable manually between a first position wherein said fuse drawers can be opened and a second position wherein opening thereof is obstructed, said cam follower rods have enlarged diameter portions and said interlock also includes means responsive to said fuse drawer obstructing means being in said first position for preventing displacement of either of said cam follower rods by its associated cam and including a reciprocable interlocking bar having keyhole opening receiving said cam follower rods, said enlarged diameter being greater than the width of the rectangular portion of said keyhole openings and less than the diameter of the circular portion of said keyhole openings.

The interlock of claim 3 between said pair of circuit interrupters and a plurality of drawout fuse drawers reciprocable in a common plane and including a plurality of mechanically ganged members operable manually between a first position wherein they prevent reciprocation of said drawers and a second position wherein said drawers can be reciprocated. and means responsive to said ganged members being in said second position for preventing displacement of either of said cam followers by its associated cam, said last-named means also being responsive to said maximum displacement of either of said cam followers for preventing movement of said ganged members from said first to said second position.

8. The interlock of claim 7 wherein each of said cam followers has an enlarged diameter portion and said means for preventing displacement of either of said cam followers includes said enlarged diameter portions of said cam followers and an elongated reciprocable interlocking bar having keyhole openings therein receiving said cam followers. said enlarged diameter being greater than the width of the rectangular portion of said keyhole openings and less than the diameter of the circular portion of said keyhole openings.

9. The interlock of claim 8 and including parallel crank linkage means operatively connecting said ganged members and said interlocking bar for reciprocating said interlocking bar between a position wherein said cam followers are in said circular portion of said keyhole openings when said ganged members are in said first position and a position wherein said cam followers are in said rectangular portion of said keyhole openings when said ganged members are in said second position.

10. The interlock of claim 9 wherein said ganged members are interfering arms rotatable about parallel shafts between said first position wherein they obstruct withdrawal of said fuse drawers and said second position wherein they do not interfere with withdrawal of said fuse drawers, and said parallel crank linkage means includes a connector rod affixed to said interlocking bar, and a plurality of first parallel crank arms pivotally connected at spaced points to said connector rod and operatively connected to said parallel shafts.

11. The interlock of claim 10 and including means for guiding said interlocking bar so that it can only reciprocate longitudinally, and wherein said parallel crank linkage means also includes a plurality of second crank arms each of which is affixed at one end to one of said parallel shafts and is pivotally connected at its other end to one of said first crank arms, whereby actuation of said ganged members between said first and second positions results in longitudinal movement of said interlocking bar.

12. The interlock of claim 8 wherein said operating members are rotatable shafts and said cams are eccentric and affixed to said operating members and including threaded adjusting means extending longitudinally of and affixed by screw threads to one end of said cam followers and engaging said cams for selectively changing the length of said cam followers. whereby the position of said rocking bar relative to said stop member may be adjusted.

13. The interlock of claim 12 wherein said cam followers are generally parallel elongated rods and are displaced longitudinally by said eccentric cams and also including means for resiliently urging said cam follower rods against said cams, and means for pivotaliy connecting said rocking bar to said cam follower rods.

14. The interlock of claim 8 wherein said cam followers are generally parallel elongated rods and are displaced longitudinally by said cams and also including means for resiliently urging said cam follower'rods against said cams, and means for pivotaliy connecting said rocking bar to said cam follower rods.

UNITED S'IA'IES PA'IEN'I OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 562, 452 Dated February 9, 1971 Inventor(s) Thomas H. Keogh and Adolph E. Krupit It: is certified that error appears in the above-identified pat and that said Letters Patent: are hereby corrected as shown below:

Co1umn 9, lines 39-H0, "maximum opening diplacement" sho1 be ---maximum displacment---. I

Signed and sealed this 15th day of June 1971.

(S-EAL) Attest: EDWARD M.F LETCHER,JR. WILLIAM E. SCHUYLE: Atte sting Officer Commissioner of Pa. 

1. An interlock for a pair of circuit interrupters each having a rotatable shaft for actuating it between open and closed positions comprising, in combination: a pair of eccentric cams each of which is operatively connected to and adapted to be rotated by one of said rotatable shafts; a pair of generally parallel elongated rod cam followers; means for resiliently urging each of said cam followers against one of said cams, said cam upon rotation displacing said cam follower rod longitudinally and effecting maximum displacement of said cam follower rod when said interrupter is in closed position and minimum displacement thereof when said interrupter is in open position; an elongated rocking bar pivotally connected adjacent its ends to said cam follower rods; stationary stop means intermediate the ends of said rocking bar for permitting said rocking bar to pivot when either cam follower rod is displaced by the corresponding cam and for preventing translation of said rocking bar in a direction transverse to its length when either cam follower rod is at said maximum displacement, whereby both of said circuit interrupters cannot be closed simultaneously; means for resiliently urging said cam follower rods against said cams; and adjusting means extending longitudinally of and threaded to one end of said cam follower rods and engaging said cams for selectively changing the length of said cam follower rods, whereby the position of said rocking bar relative to said stop means may be adjusted.
 2. An interlock for a pair of circuit interrupters each having an operating member for actuating it between open and closed positions comprising, in combination: a pair of cams each of which is operatively connected to and adapted to be rotated by one of said operating members; an elongated cam follower rod engaging each said cam, said cam upon rotation displacing said cam follower lOngitudinally and having a limit position thereon providing maximum displacement of said cam follower when said interrupter is in closed position; an elongated rocking bar pivotally connected adjacent its ends to said cam followers; and means including a stationary defeater pin stop member positioned adjacent said rocking bar intermediate its length on the side thereof away from said cams for permitting said rocking bar to pivot about said stop member when either cam follower is displaced by the corresponding cam and for preventing transverse translation of said rocking bar when either cam follower is at said maximum displacement, whereby both of said circuit interrupters cannot be closed simultaneously, said defeater pin stop member being manually retractable to a position wherein it does not interfere with movement of said rocking bar, whereby both of said circuit interrupters can be closed when it is so desired.
 3. An interlock for a pair of circuit interrupters each having an operating member for actuating it between open and closed positions and between said circuit interrupters and a fuse drawer reciprocable between open and closed positions comprising, in combination; a pair of cams each of which is operatively connected to and adapted to be rotated by one of said operating members; a pair of cam followers each of which engages one of said cams, said cam upon rotation displacing said cam follower and effecting maximum displacement thereof when said interrupter is in closed position; an elongated rocking bar operatively connected adjacent its ends to said cam followers; stop means intermediate the ends of said rocking bar for permitting said rocking bar to pivot when either cam follower is displaced by the corresponding cam and for preventing transverse translation of said rocking bar when either interrupter is closed and the corresponding cam follower is at said maximum displacement, whereby both of said circuit interrupters cannot be closed simultaneously, and means responsive to said maximum opening displacement of either of said cam followers for preventing opening of said fuse drawer.
 4. An interlock in accordance with claim 3 wherein said means for preventing opening of said fuse drawer includes a member operable manually between a first position wherein said fuse drawer can be opened and a second position wherein it obstructs opening of said fuse drawer, and wherein said interlock also includes means responsive to said member being in said first position for preventing displacement of either of said cam followers by its associated cam, whereby neither of said interrupters can be closed when said fuse drawer is open.
 5. An interlock in accordance with claim 3 between said pair of circuit interrupters and a plurality of drawout fuse drawers reciprocable in a common claim wherein said cams are eccentric and said cam followers are generally parallel elongated rods and are displaced longitudinally by said eccentric cams and are pivotally connected adjacent the ends of said rocking bar and also including means responsive to said maximum displacement of either of said cam follower rods for obstructing opening of said plurality of drawout fuse drawers.
 6. An interlock in accordance with claim 5 wherein said means for obstructing opening of said plurality of fuse drawers is operable manually between a first position wherein said fuse drawers can be opened and a second position wherein opening thereof is obstructed, said cam follower rods have enlarged diameter portions and said interlock also includes means responsive to said fuse drawer obstructing means being in said first position for preventing displacement of either of said cam follower rods by its associated cam and including a reciprocable interlocking bar having keyhole opening receiving said cam follower rods, said enlarged diameter being greater than the width of the rectangular portion of said keyhole openings and less than the diameter of the circular portion of said keyhole openings.
 7. The interlock of claim 3 between said pair of circuit interrupters and a plurality of drawout fuse drawers reciprocable in a common plane and including a plurality of mechanically ganged members operable manually between a first position wherein they prevent reciprocation of said drawers and a second position wherein said drawers can be reciprocated, and means responsive to said ganged members being in said second position for preventing displacement of either of said cam followers by its associated cam, said last-named means also being responsive to said maximum displacement of either of said cam followers for preventing movement of said ganged members from said first to said second position.
 8. The interlock of claim 7 wherein each of said cam followers has an enlarged diameter portion and said means for preventing displacement of either of said cam followers includes said enlarged diameter portions of said cam followers and an elongated reciprocable interlocking bar having keyhole openings therein receiving said cam followers, said enlarged diameter being greater than the width of the rectangular portion of said keyhole openings and less than the diameter of the circular portion of said keyhole openings.
 9. The interlock of claim 8 and including parallel crank linkage means operatively connecting said ganged members and said interlocking bar for reciprocating said interlocking bar between a position wherein said cam followers are in said circular portion of said keyhole openings when said ganged members are in said first position and a position wherein said cam followers are in said rectangular portion of said keyhole openings when said ganged members are in said second position.
 10. The interlock of claim 9 wherein said ganged members are interfering arms rotatable about parallel shafts between said first position wherein they obstruct withdrawal of said fuse drawers and said second position wherein they do not interfere with withdrawal of said fuse drawers, and said parallel crank linkage means includes a connector rod affixed to said interlocking bar, and a plurality of first parallel crank arms pivotally connected at spaced points to said connector rod and operatively connected to said parallel shafts.
 11. The interlock of claim 10 and including means for guiding said interlocking bar so that it can only reciprocate longitudinally, and wherein said parallel crank linkage means also includes a plurality of second crank arms each of which is affixed at one end to one of said parallel shafts and is pivotally connected at its other end to one of said first crank arms, whereby actuation of said ganged members between said first and second positions results in longitudinal movement of said interlocking bar.
 12. The interlock of claim 8 wherein said operating members are rotatable shafts and said cams are eccentric and affixed to said operating members and including threaded adjusting means extending longitudinally of and affixed by screw threads to one end of said cam followers and engaging said cams for selectively changing the length of said cam followers, whereby the position of said rocking bar relative to said stop member may be adjusted.
 13. The interlock of claim 12 wherein said cam followers are generally parallel elongated rods and are displaced longitudinally by said eccentric cams and also including means for resiliently urging said cam follower rods against said cams, and means for pivotally connecting said rocking bar to said cam follower rods.
 14. The interlock of claim 8 wherein said cam followers are generally parallel elongated rods and are displaced longitudinally by said cams and also including means for resiliently urging said cam follower rods against said cams, and means for pivotally connecting said rocking bar to said cam follower rods. 